Library storage problem

Hello everyone. I'm writing here hoping someone will be able to help me with a problem I recently had with a library project archive. In the last 2 months I worked on a main project and other small ones in a single library on FCP without thinking about the little storage of my computer (MacBook Pro 250gb). Since my laptop storage was full, I deleted from the library all the small projects I didn't need anymore and the related clips/music etc related to them (some clips of the small projects were also used on the main one, and this ones I kept). The problem is that even if I deleted all this clips and projects I didn't need anymore, the library is still 100 gb as before, and I cannot explain myself why. Is it like a bin or something like this of FCP where I can completely deleted the already deleted clips and projects of the library or is it another solution to free up some space without loosing the main project I'm working on ? Thanks to everyone for the help. 

1- Verify the Library is set to store all clips internally.
2- Delete all render files.